Felt



Patented May 10, 1932 UNITED STATES PATENTLOFFICE PHILIP w. conwrsn, or KENMORE, NEW Yonx, ASSIGNOR, BY. mnsnn assrcnmnnrs, T CERTAIN-TEE!) rnonucrs oonronarron, A conronarron or MARYLAND FELT No Drawing.

This application is a continuation in part E of my copending application Serial No.

21,727, filed ,April 8, 1925and also contains features which are disclosed in my co-pending application Serial No. 130,361,'which is a continuation in part of said application, Serial No. 21,727, filed April 8, 1925, and of this present application. 0 J

Roofing felt has been made heretofore, almost exclusively from rag stock because no other satisfactory material has been available.

for that purpose. The supply of rag stock is limited and it is, therefore, comparatively expensive. To reduce the cost,'there is sometimes used'ordinary paper or wood pulp,

- whether produced by mechanical or chemical 3 disintegration, consisting essentially of ultimate fibres of cellulose which are'much too fine to possess the necessary absorlo'ent'prop-v erties'for asphalt or pitch. Such fibres'mat readily into a dense mass which lacks porosity, the resulting sheets being entirely difierentin character from the porous felt required in industries wherein properly saturated and water-proofed bases must be used. The usual 40 addition of paper pulp to rag stock to pro; an addition does not reduce the cost sufiicient- 1y to offset the inferior saturating qualities resulting.

It is the object of the present invention to 5 provide a cheaper and more satisfactory felt 'material for the purpose mentioned, which saturates more readily than ordinary rag felt, or' raga-nd paper felt. :The material isderived from wood but it is entirely difier'ent in nature and properties from ordinary paduce a satisfactory felt is about 10% but such Application and m 8, 1925. Serial no. 42,316.

' per or wood pulp, mechanical or chemical, and possesses the necessary characteristics to ensure absorption of saturating materials and thus to provide a suitable foundation for roofing, floor'covering or similar bases.

Other objects and advantages of the invention will be apparent. when reference is had to the following specification in which the preferred embodiments are described to exemplify the method and product.

I have discovered that a satisfactory. felt-. ing material-can be prepared by suitably treating wood chips so that the resins and lignins therein are only partially removed, leaving the fibre in the form of bundles eemented together by the natural contents of the wood. These bundles are to be distinguished from the ultimate fibres such as are obtained in the manufacture of the usual chemical wood pulp, since they can be formed into a. felt having great porosity and capillary attraction for molten saturating or impregnating; material as well as hightensile strength. Various woods-may be utilized in preparing the fibre bundles but the so called coniferous woods, such as pine, fir, hemlock, cedar and spruce are especially satisfactory sources of thematerial because of the length and other characteristics of the fibres incorporated therein.

- To prepare the material the wood is chipped in the usual log chipper or'similar machine. Preferably the chips are subjected to a preliminary steamingin anysuitableapparatusto soften the binding material and are then impregnated thoroughly with an alkaline solution containing for example,

sodium hydroxide- The impregnated chips are then cooked in the alkaline solution with steam at an elevated temperature and pressure until the desired effect is obtained, This is accomplished when the chips are so digested that they can be disintegrated readily into masses of long fibre bundles which when 7 washed and beaten in water intertwine and felt. Itis important to note that the opera tion must be conducted to avoid disintegration into ultimate fibres as is the case in the manufacture of paperpulp. While it is preferable to first steam and impregnate thechips,

these steps can be omitted, the cooking being.

conducted direct with steam as soon as the physical condition but in fact they have undergone an important change as they are soft and spongy and the fibres have acquired remarkable capillary properties which are not noticeable in the uncooked wood. The treatment with alkaline solutionsremoves a mod gesterh they are apparently in their original If desired the operation described above can be condensed into a single operation lwhich produces the same result, but is somewhat. more time consuming. This is to place 100 parts of wood chips in a digester and immediately add thereto approximately 250 parts by weight of water and about 8 parts I by weight-of sodium hydroxide. The entire 'mass is immediately cooked under pressure of 60 to 120 pounds per square inch at a tem- 'perature of approxiniately160 from 5 to 12 erate amountof-resi'ns and ,lignins, and softens the remaining material'whi ch originally between the fibre bundles is loosened without f disintegrating the-mass into the'ultimate cel-,

lulose fibres-" The loosening of-the; bond-fa cilitates the separation of the fibre bundles be referred to- Whenfsepara'ted the bundles are soft and fiufiy and can be felted after beating to produce a strong and porous-sheet.

' Y As anexample of the method-herein dis hours. The chips are then ready 'to be disintegrated and treated as described above The proportion ofsod'ium hydroxide used in this yinethod will vary from 4%l14%, depending. bonded the fibres together. -xThus the, bond 'uponthe wood used.

.develop absorptive properties when treated i'vith alkalinesolutions at elevated tempera-rv turos, is'suitablc for the purpose of this in -"Yent'ion,' but it-is preferred to use coniferous wood, especially pine, because of its suitfa-' ability and. low cost. Any

alkaline" solution which will soften the wood and develop ab- "sorptivo properties in the same is suitable 'for the purpose of this invention, but it is closed 100 parts of pine wood" chipsofapproximately 1" inlength are placed in a di"-:

to be understood that the invention is lot to be limited to the use of sodium hydroxide.

gester and-steamed for approximately %.of

up to 100 pounds per square inch,;'w'ith an excess of sodium hydroxide solution of 5% or less concentration. The impregnation Alkaline solutions of sodium sulphite have iproducedsimilar results and other alkaline solutions, suchassodiiuncarbonate, calcium hydroxide and" the like can be used in combination' with similar results. The proporperiod during which the chips are thoroughly impregnated continuesfor approximately of an houriwhen the excess liquid is drawn oif to bereused on subsequent batches. Only a suflicient quantity for cooling purposes now remains in the chips so thatth'e dry weight of sodium hydroxide present, equals 14% or less of the dry weight of the wood chips. The

amount of sodium hydroxide used in cooking will vary somewhat with the nature of the wood, especially with the resin content of the wood,-but will seldom be below 4% or above 14%. -,Following the impregnating period, steam is allowed to enter the'digest er 6 until the temperature rises to approximately 160 0-; the pressureduring this period ranging from 60 to 120 pounds per squareinch. This is known as the cook period and continues from 3 to 5 hours, depending on the nature of the chips-used. When the .cook

. or Fourdrinier period has been completed, the cooked chips are removed from the digester and washed. The chips are then partly disintegrated, shredded or torn apart by any mechanical means into fibrous bundles, washed and beaten slightly with water .and thereafter made into a sheet by any known felting apparatus.

An ordinary paper machine as'used atpresent in felt manufacture, such as the cylinder is suitable for this purp pose. 1 a,

ti'on' of water to the chips may be varied ac cording to the material used.

The method produces a sheet 'of suflicient strength and pliabilityto be rolled and treated as is usual in preparing saturating felt. The

sheet possesses high capillarity not only by virtue of the 'voids formed in the fibres themselves, but also by virtue of the formation of numerous voids between the fibre bundles resulting in high absorptive characteristics in i the product. The cooking process is essential for the production of such capillarity and of pliability in the product, and the disintegration or tearing apart of the fibre bundles with water is desirable for the production of satisfactory bonding of the fibre bundles and the production of satisfactory tensile strength in the product. Material prepared as herein described produces a sheet which will absorb saturants at amore rapid rate and to a much higher degree than fibrous material obtained from ordinary pulp. A sheet made accord.- ing to the described method is composed of long absorbent fibres which in additionto their absorptive qualities, due to their length,

will interlock causing numerous openings there-between for 'quick penetration of the saturating material. The felt made according to this invention may moreover absorb 300% or more of its weight of roofing asphalt as compared with the ordinary rag felt which V usually absorbs only 180% or less of its weight.

The fibrous sheet material made as herein described may be too absorbent for some purposes, and toretard the absorption, rag fibres or waste paper may be intermixed when felting the sheet. The quantities of the various fibres used depends upon the intended pur pose and use of the material.

Matter not claimed in this application is made part of and claimed in my co-pending applications Serial Numbers 130,361 and 180,362 filed August 19, 1926.

Obviously the present invention is not restricted to the details of the particular emv bodiment thereof herein described. Moreover, it is not indispensable that all the features of the invention be used conjointly since they may be employed advantageously in various combinations and sub-combinations.

Having described one embodiment of the invention I claim:

The method of making felt which comprises preliminarily steammg wood chips, im-

pregnating the same under pressure with excess of sodium hydroxide solution of 5% or less concentration, draining oil' the liquor after impregnation to an extent to leave an amount containing 4% to 14% of alkali in relation to the weight of the chips, cooking the chips with this liquor under pressure under such conditions as to softenthem and incompletely release the bond between the fibres to maintain the fibres in their natural positions in the chips, and then shredding the chips to separate the same for the most part into bundles of the fibres, and matting the same into sheets.

In testimony whereof, I affix my signature. PHILIP W. CODWISE. 

